JP2014153652A - Carrier for electrostatic latent image developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for an electrostatic latent image developer that has toner supply ability to support high-speed development and high durability, a developer having the carrier, an image forming apparatus, a process cartridge, and an image forming method using a carrier.SOLUTION: A carrier for an electrostatic latent image developer includes core material particles having magnetism, and a resin coating layer containing conductive fine particles that coats the surface of each of the core material particles; and has a BET specific surface area of 0.8 m/g or more and 1.6 m/g or less.

Description

The present invention relates to a carrier for developing an electrostatic latent image used in a two-component developer used in electrophotography and electrostatic recording, an electrostatic latent image developer, a color toner developer, and a replenishing development using the carrier. The present invention relates to an agent, an image forming method, a process cartridge including an electrostatic latent image developer, and an image forming apparatus.

  In electrophotographic image formation, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductive substance, and a charged toner is attached to the electrostatic latent image to form a toner image. After that, the toner image is transferred to a recording medium and fixed to form an output image. In recent years, the technology of copying machines and printers using an electrophotographic system is rapidly expanding from monochrome to full color, and the full color market tends to expand.

  In full-color image formation, generally, color toners of three colors of yellow, magenta, and cyan or four color toners obtained by adding black to this are laminated to reproduce all colors. Therefore, in order to obtain a clear full color image with excellent color reproducibility, it is necessary to smooth the surface of the fixed toner image to reduce light scattering. For these reasons, the image gloss of conventional full-color copying machines and the like is often 10 to 50% of medium to high gloss.

  In general, as a method for fixing a dry toner image on a recording medium, a contact heating fixing method in which a roller or belt having a smooth surface is heated and pressed against the toner is frequently used. Such a method has high thermal efficiency and enables high-speed fixing, and can give gloss and transparency to a color toner image. On the other hand, the surface of the heat fixing member and the molten toner are brought into contact with each other under pressure. Then, in order to peel off, a so-called offset phenomenon occurs in which a part of the toner image adheres to the surface of the fixing roller and is transferred onto another image.

  In order to prevent such an offset phenomenon, the surface of the fixing roller is formed of silicone rubber or fluorine resin having excellent releasability, and further, an oil for preventing toner adhesion such as silicone oil is applied to the surface of the fixing roller. This method is generally adopted. However, such a method is extremely effective in preventing toner offset, but requires a device for supplying oil, and there is a problem that the fixing device is increased in size.

  For this reason, in monochrome image formation, an oilless system in which viscoelasticity at the time of melting is large and toner containing a release agent is used so that the melted toner does not break internally, so that no oil is applied to the fixing roller, or There is a tendency to adopt a system in which a small amount of oil is applied.

  On the other hand, in full-color image formation, as in the case of monochrome image formation, an oilless system tends to be employed for the purpose of downsizing the fixing device and simplifying the configuration. However, in full-color image formation, it is necessary to reduce the viscoelasticity of the toner at the time of melting in order to smooth the surface of the fixed toner image. Therefore, offset occurs more than in the case of monochrome image formation without gloss. This makes it difficult to adopt an oilless system. Further, when a toner containing a release agent is used, adhesion of the toner is increased and transferability to a recording medium is decreased. Furthermore, there is a problem in that the durability is lowered due to the occurrence of toner filming and a decrease in chargeability.

  On the other hand, as a carrier, prevention of toner filming, formation of a uniform surface, prevention of surface oxidation, prevention of decrease in moisture sensitivity, extension of developer life, prevention of adhesion to the surface of a photoreceptor, photosensitivity For the purpose of protecting the body from scratches or abrasion, controlling the charge polarity, adjusting the charge amount, etc., the carrier core material surface is coated with a resin having a low surface energy, such as a fluororesin or a silicone resin. Long life has been achieved.

Examples of carriers coated with low surface energy resin include:
A carrier coated with a room temperature curable silicone resin and a positively chargeable nitrogen resin described in Japanese Patent Application Laid-Open No. 55-127469 of Patent Document 1,
A carrier coated with a coating material containing at least one modified silicone resin described in JP-A-55-157751 of Patent Document 2;
A carrier having a resin coating layer containing a room temperature curable silicone resin and a styrene / acrylic resin described in JP-A-56-140358 of Patent Document 3;
A carrier in which the surface of the core particles described in JP-A-57-96355 of Patent Document 4 is coated with two or more layers of silicone resin so that there is no adhesion between the layers,
A carrier in which a silicone resin is applied in multiple layers on the core particle surface described in JP-A-57-96356 of Patent Document 5,
A carrier whose surface is coated with a silicone resin containing silicon carbide described in JP-A-58-207054 of Patent Document 6;
A positively chargeable carrier coated with a material having a critical surface tension of 20 dyn / cm or less described in JP-A No. 61-110161 of Patent Document 7;
Examples thereof include a carrier coated with a coating material containing a fluorine alkyl acrylate described in JP-A-62-273576 of Patent Document 8 and a developer comprising a toner containing a chromium-containing azo dye.

  Further, in order to improve the charge imparting property to the toner, a carrier having a small particle diameter is often used. However, the carrier having a small particle diameter is likely to adhere to the carrier, and the photoconductor, the fixing roller, etc. are damaged. In order to prevent the carrier adhesion, a core material having a strong magnetic force is used.

As an example using core particles with a small BET specific surface area and strong magnetic force,
It is disclosed in Japanese Patent Application Laid-Open No. 2005-309184 of Patent Document 9, Japanese Patent No. 4544099 of Patent Document 10, Japanese Patent No. 4621639 of Patent Document 11, and Japanese Patent Application Laid-Open No. 2008-40271 of Patent Document 12.

  However, these carriers have a low toner holding / conveying capability, and due to a local lack of toner supply performance, when forming an image having a solid portion in a halftone, the solid portion of the solid portion is formed by an edge effect. There may be a halo image or a ghost image in which the surrounding halftone latent image is emphasized and the portion is whitened.

Japanese Patent Application Laid-Open No. 2011-253007 of Patent Document 13 discloses a coat carrier having a large BET specific surface area. However, the coat layer does not contain conductive fine particles, and the wear resistance of the coat layer is low. Is.

  JP-A-2006-259179 of Patent Document 14, JP-A-2009-53545 of Patent Document 15, and JP-A-2009-300531 of Patent Document 16 describe a coated carrier rather than the BET specific surface area of the core material. A carrier is disclosed in which the contact area with the toner is increased by increasing the BET specific surface area of the toner to improve the charge imparting ability to the toner and improve the toner holding ability.

However, recent image forming apparatuses are required to reduce the environmental waste load due to high speed and long life, and to reduce the printing cost per sheet, and a carrier with higher durability is required. These carriers still have a small BET specific surface area and cannot meet the above requirements.
In addition, with the expansion of the production printing market, it is necessary to achieve both high durability and high image quality, and it is essential to design carriers that meet these requirements.

The present invention has a toner supply capability capable of high-speed development and a highly durable electrostatic latent image developer carrier, a developer having the carrier, an image forming apparatus, a process cartridge, and an image using the carrier. An object is to provide a forming method.

As a result of intensive studies by the present inventors, it is possible to dramatically increase the BET specific surface area of the carrier by coating the surface of the magnetic core particles with a resin coating layer containing conductive fine particles. It has been found that the transportability is improved and the durability is improved, and the charging property and resistance with time are stabilized, and the present invention has been completed.
That is, the said subject is solved by following (1)-(10) of this invention.
(1) “A carrier for an electrostatic latent image developer having a magnetic core material particle surface coated with a resin coating layer containing conductive fine particles, and having a BET specific surface area of 0.8 m ² / g or more 1 A carrier for an electrostatic latent image developer, wherein the carrier is .6 m ² / g or less ”,
(2) “The carrier for an electrostatic latent image developer according to (1) above, wherein an average primary particle size of the conductive fine particles is 0.35 μm or more and 0.65 μm or less”;
(3) The item (1) or (2), wherein the conductive fine particles are contained in an amount of 0.016 parts by weight to 0.040 parts by weight with respect to 1 part by weight of the core particles. A carrier for an electrostatic latent image developer as described in "
(4) “When the BET specific surface area of the carrier is (B1) and the BET specific surface area of the core is (B2), the specific surface area ratio (B1 / B2) satisfies the relationship of the following formula (1): The electrostatic latent image developer carrier according to any one of Items (1) to (3), wherein:

」、
（５）「前記第（１）項乃至第（４）項のいずれかに記載のキャリア及びトナーを有することを特徴とする二成分現像剤」、
（６）「前記トナーは、カラートナーであることを特徴とする前記第（５）項に記載の現像剤」、
（７）「キャリア及びトナーを含む補給用現像剤であって、キャリア１質量部に対してトナーを２〜５０重量部含有するものであり、前記キャリアが前記第（１）項乃至第（４）項のいずれかに記載のキャリアであることを特徴とする補給用現像剤」、
（８）「静電潜像担持体と、該潜像担持体を帯電させる帯電手段と、該潜像担持体上に静電潜像を形成する露光手段と、該静電潜像担持体上に形成された静電潜像を、前記第（５）項乃至第（７）項のいずれかに記載の現像剤を用いて現像してトナー像を形成する現像手段と、該静電潜像担持体上に形成されたトナー像を記録媒体に転写する転写手段と、該記録媒体に転写されたトナー像を定着させる定着手段とを有することを特徴とする画像形成装置」、
（９）「静電潜像担持体、該感光体の表面を帯電させる帯電部材と、前記静電潜像担持体上に形成された静電潜像を前記第（５）項乃至第（７）項のいずれかに記載の現像剤を用いて現像する現像部と、前記静電潜像担持体をクリーニングするクリーニング部材を有することを特徴とするプロセスカートリッジ」、
（１０）「静電潜像担持体上に静電潜像を形成する工程と、該静電潜像担持体上に形成された静電潜像を、前記第（５）項乃至第（７）項のいずれかに記載の現像剤を用いて現像してトナー像を形成する工程と、該静電潜像担持体上に形成されたトナー像を記録媒体に転写する工程と、該記録媒体に転写されたトナー像を定着させる工程とを有することを特徴とする画像形成方法。

"
(5) “Two-component developer comprising the carrier and toner according to any one of (1) to (4)”,
(6) "The developer according to item (5), wherein the toner is a color toner",
(7) “A replenishment developer including a carrier and a toner, the toner containing 2 to 50 parts by weight of the toner with respect to 1 part by weight of the carrier, wherein the carrier is the above-mentioned items (1) to (4). A developer for replenishment characterized in that it is a carrier according to any one of items 1),
(8) “An electrostatic latent image carrier, charging means for charging the latent image carrier, exposure means for forming an electrostatic latent image on the latent image carrier, and on the electrostatic latent image carrier And developing means for developing the electrostatic latent image formed on the surface using the developer according to any one of (5) to (7) to form a toner image, and the electrostatic latent image. An image forming apparatus comprising: a transfer unit that transfers a toner image formed on a carrier to a recording medium; and a fixing unit that fixes the toner image transferred to the recording medium.
(9) “The electrostatic latent image carrier, the charging member for charging the surface of the photosensitive member, and the electrostatic latent image formed on the electrostatic latent image carrier are the items (5) to (7). A process cartridge having a developing section for developing using the developer according to any one of the paragraphs 1) and a cleaning member for cleaning the electrostatic latent image carrier.
(10) “The step of forming an electrostatic latent image on the electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier are classified into the items (5) to (7 And a step of forming a toner image by developing using the developer according to any one of items 1), a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and the recording medium And a step of fixing the toner image transferred to the image.

As will be understood from the following detailed and specific description, according to the present invention, a carrier having a high BET specific surface area can be provided by highly filling the core material particles with conductive fine particles.
The carrier of the present invention is excellent in chargeability and transportability of toner, can provide a high-quality image with little halo and ghost images, and has high durability due to high film strength.
Furthermore, because of high durability, it is possible to suppress environmental fluctuations of charging, and image density fluctuations, background contamination, and in-machine contamination due to toner scattering do not occur even in various usage environments.
In addition, a highly reliable development method and an image forming apparatus can be provided.

It is a figure explaining the cell for measuring volume specific resistance in the present invention. It is a figure which shows an example of the process cartridge of this invention. It is a figure explaining a hello image. It is a figure explaining a ghost image.

The carrier for an electrostatic latent image developer of the present invention will be described in detail.
In the carrier of the present invention, the surface of the core particle having magnetism is coated with a resin coating layer containing conductive fine particles, and the BET specific surface area is 0.8 m ² / g or more and 1.6 m ² / g or less. It is a carrier for an image developer.

The BET specific surface area is an index representing the surface property of a substance. Generally, when the surface is smooth, the value of the BET specific surface area is low, and when the surface is rough, the value of the BET specific surface area is large. This value is important because the toner charge amount is generated by contact friction with the carrier.
In the present invention, it is considered that by providing a resin coating layer containing conductive fine particles, impact resistance is improved and durability is improved, and further, since the surface of the carrier particles is not changed, the charging ability is stabilized over time.
In other words, the conductive fine particles mainly function as a resistance adjusting agent, but by using conductive fine particles in which a conductive material is coated on a metal substrate, the conductive particles having high hardness when the carrier particles collide in the developing machine. This is presumably because the frequency of contact between the fine particles increases, leading to reduced wear of the resin coating layer containing conductive fine particles.

The carrier of the present invention has an extremely larger surface area than the conventional coated carrier and has a BET specific surface area of 0.8 m ² / g or more and 1.6 m ² / g or less, and the BET specific surface area is 0.9 m. More preferably, it is ² / g or more and 1.5 m ² / g or less.
When the BET specific surface area is less than 0.8 m ² / g, the effect of reducing wear of the resin coating layer by the conductive fine particles is small, the resin coating layer is scraped, carrier resistance is lowered, and carrier scattering occurs. On the other hand, when the BET specific surface area exceeds 1.6 m ² / g, the toner spent on the coating film advances, charging ability is lowered, density fluctuation occurs, and this causes a problem.

  The BET specific surface area of the carrier can be adjusted by the BET specific surface area of the core material and the particle size and content of the conductive fine particles. The BET specific surface area is measured using, for example, TriStar 3000 (manufactured by Shimadzu Corporation). be able to.

<Conductive fine particles>
The conductive fine particles preferably have an average particle size of 0.35 (μm) or more and 0.65 (μm) or less. If the average particle size is less than 0.35 (μm), the conductive fine particles are likely to aggregate, making it difficult to disperse into single particles, and when present as a carrier, they will exist as large conductive fine particle clusters. The conductive fine particles are easily detached from the resin layer. On the other hand, when the average particle size exceeds 0.65 (μm), it is easy for separation to occur due to stress due to stirring or the like.
The average particle diameter can be measured using, for example, Nanotrac UPA series (manufactured by Nikkiso Co., Ltd.).

  The content of the conductive fine particles is preferably 0.016 parts by weight or more and 0.040 parts by weight or less with respect to 1 part by weight of the core particles. If it is less than 0.016, the resin coating layer containing the conductive fine particles undergoes film scraping over time, causing a decrease in resistance, and carrier scattering occurs. On the other hand, if it exceeds 0.040 parts by weight, the toner spent on the carrier particles advances and the charging ability decreases, so that the density fluctuation is likely to occur.

The powder specific resistance of the conductive fine particles is preferably 3 to 20 (Ωcm). The resistance value of the carrier is adjusted mainly by the prescription amount of the conductive fine particles functioning as a resistance adjusting agent. However, when the powder specific resistance of the conductive fine particles is 3 (Ωcm) or less, the prescription amount decreases, and the carrier The durability of the steel tends to decrease. In addition, the particle diameter of the conductive fine particles is increased, and the separation from the resin coating layer is likely to occur.
On the other hand, if the powder specific resistance is 20 (Ωcm) or more, the amount of prescription increases, so the dispersibility in the resin deteriorates, and it exists as a large conductive fine particle lump, resulting in separation from the resin layer. It becomes easy.
The powder specific resistance of the conductive fine particles can be measured using, for example, an LCR meter (manufactured by Yokogawa Hewlett Packard).

Examples of the conductive fine particles include metal powder, titanium oxide, tin oxide, zinc oxide, alumina, indium tin oxide (ITO), titanium oxide fine particles surface-treated with indium oxide doped with carbon black or antimony, ITO Or the alumina fine particle etc. which surface-treated with phosphorus dope tin etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Since the conductive fine particles have tough properties, they are strong against this external force, do not cause crack wear, and can maintain high durability over a long period of time.

  The conductive fine particles may be subjected to a surface treatment. By performing such treatment, the conductive fine particles can be uniformly and firmly fixed to the resin coating layer, so that the resistance adjusting effect can be sufficiently exhibited. Amino silane coupling agents, methacryloxy silane coupling agents, vinyl silane coupling agents, and mercapto silane coupling agents can be used.

<Resin coating layer>
The resin coating layer of the present invention fixes conductive fine particles to the surface of the core material particles, and completely covers the surface of the core material particles together with the conductive fine particles, thereby adjusting the carrier resistance.
As the resin constituting the resin coating layer, an acrylic resin and a silicon resin can be used in combination.
Acrylic resin is a toner that is easy to spend due to its high surface energy and high wear resistance because it has strong adhesiveness and can strongly adhere conductive particles with large particle size to the surface of the core particles and has low brittleness. When the toner is used, the toner component may be spent and problems such as a decrease in charge amount due to accumulation on the carrier surface may occur.
Therefore, this problem can be solved by using a silicone resin having a low surface energy and difficult to spend toner components.

However, since the silicone resin has weak adhesiveness and high brittleness, it also has a weak point that the wear resistance is inferior. Therefore, it is important to obtain a good balance between the properties of these two types of resin, which makes it difficult to spend. It is possible to obtain a resin layer having wear characteristics.
Although the resin coating layer of the present invention depends on the resin to be used, it is preferable to contain 250 parts by weight to 500 parts by weight of the silicone resin with respect to 100 parts by weight of the acrylic resin, and 300 parts by weight to 400 parts by weight. Is more preferable.

The acrylic resin may be any resin having an acrylic component generally known in the past, and is not particularly limited. However, the acrylic resin is not limited to silicon from the viewpoint of compatibility with the silicone resin and prevention of toner spent. A modified acrylic resin is preferred.
Although it is possible to use the acrylic resin alone, it is also possible to use at least one other component that undergoes a crosslinking reaction at the same time. Examples of other components that undergo a crosslinking reaction include amino resins and acidic catalysts. However, it is not limited to this.

Examples of the amino resin include, but are not limited to, guanamine, melamine resin, and the like. In addition, as the acidic catalyst, any one having a catalytic action can be used, for example, a reactive group such as a fully alkylated type, a methylol group type, an imino group type, or a methylol / imino group type. However, it is not limited to these.

The acrylic resin is preferably crosslinked with an amino resin.
When this acrylic resin is crosslinked with an amino resin, fusion between the resin layers can be suppressed while maintaining appropriate elasticity.
The amino resin is not particularly limited, but a melamine resin and a benzoguanamine resin are preferable because the charge imparting ability of the carrier can be improved. Further, when it is necessary to control the charge imparting ability of the carrier, a melamine resin and / or a benzoguanamine resin and another amino resin may be used in combination.

  As the acrylic resin capable of crosslinking with the amino resin, those having a hydroxyl group and / or a carboxyl group are preferred, and those having a hydroxyl group are more preferred. Thereby, the adhesiveness / adhesiveness with the core material particles and the conductive fine particles can be further improved, and the dispersion stability of the conductive fine particles can also be improved. In this case, the acrylic resin preferably has a hydroxyl value of 10 mgKOH / g or more, and more preferably 20 mgKOH / g or more.

  Examples of the silicone resin include all conventionally known silicone resins, including straight silicone consisting only of organosilosan bonds, and silicone resins modified with alkyd, polyester, epoxy, urethane, etc. This is not a limitation.

Examples of the straight silicon resin include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical, SR2400, SR2406, and SR2410 manufactured by Toray Dow Corning Silicon. In this case, it is possible to use the silicon resin alone, but it is also possible to simultaneously use other components that undergo a crosslinking reaction, charge amount adjusting components, and the like.
Further, as modified silicone resin, KR206 (alkyd modified), KR5208 (acryl modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicon Co., Ltd. , SR2110 (alkyd modified) and the like.

In the present invention, the coating resin composition preferably contains a silane coupling agent for improving the dispersion stability of the conductive fine particles.
The silane coupling agent is not particularly limited, but r- (2-aminoethyl) aminopropyltrimethoxysilane, r- (2-aminoethyl) aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane, N -Β- (N-vinylbenzylaminoethyl) -r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, Vinyltriacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, r-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium Chloride, r-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1, Examples include 3-divinyltetramethyldisilazane and methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride, and two or more of them may be used in combination.

Commercially available silane coupling agents include AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, sh6062, Z-6911, sz6300, and sz6075. , Sz6079, sz6083, sz6070, sz6072, Z-6721, AY43-004, Z-6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z -6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-69 0, Z-6940 (Toray Ltd. Silicone Co., Ltd.) and the like.
It is preferable that the addition amount of a silane coupling agent is 0.1-10 mass% with respect to a silicone resin. When the addition amount of the silane coupling agent is less than 0.1% by mass, the adhesion between the core material particles or conductive fine particles and the silicone resin is lowered, and the coating layer may fall off during long-term use. If it exceeds 10 mass%, toner filming may occur during long-term use.

  Further, the coating resin composition can contain a condensation polymerization catalyst, and examples of the condensation polymerization catalyst include a titanium catalyst, a tin catalyst, a zirconium catalyst, and an aluminum catalyst. In the present invention, these various catalysts are used. Of these, titanium diisopropoxybis (ethyl acetoacetate) is the most preferable catalyst among titanium-based catalysts that give excellent results. This is considered to be because the effect of promoting the condensation reaction of the silanol group is large and the catalyst is hardly deactivated.

By dispersing and applying the conductive fine particles in the resin composition, the conductive fine particles can be adhered to the surface of the core material particles. The content of the conductive fine particles in the resin composition is preferably 30 parts by weight or more and 200 parts by weight or less, and preferably 40 parts by weight or more and 150 parts by weight or less with respect to 100 parts by weight of the binder resin. preferable.

In the present invention, the resin coating layer has no film defects and completely covers the surface of the core particle, and the average film thickness is preferably 0.10 to 0.80 μm, and is based on the conductive fine particles. In order to form a convex part, it is more preferable that it is 0.10-0.50 micrometer thinner than the average primary particle diameter of electroconductive fine particles.
If the average film thickness is less than 0.10 μm, the resin coating layer is likely to be destroyed by use, and the film may be scraped. If the average film thickness exceeds 0.80 μm, the resin coating layer is not a magnetic substance. There is a risk that carrier adhesion may occur, and the resistance adjusting effect is not sufficiently exhibited.
The binder resin film thickness was measured by observing the cross section of the carrier particles with a transmission electron microscope, observing the coating film covering the carrier surface, and taking the average value of the film thickness as the film thickness.

<Core particles>
In the carrier of the present invention, the ratio (B1 / B2) between the BET specific surface area (B1) of the carrier and the BET specific surface area (B2) of the core is 6.0 ≦ (B1 / B2) ≦ 8.0. It is preferable to satisfy.
By satisfying 6.0 ≦ (B1 / B2) ≦ 8.0, the core material has a small BET specific surface area, that is, toner is formed by forming irregularities on the surface of the core material with few pores and strong magnetic force. A carrier having excellent holding / conveying ability can be obtained, and ghost development and generation of a halo image can be prevented.

Although the detailed mechanism that can prevent the occurrence of ghost development and halo images by setting “B1 / B2” within the above range is not known, the surface area is determined by the size of the particles and the size of the pores of the particles. In the case of a core material having a particle size, those having a small BET specific surface area have few pores and a high bulk density of the core material particles.
However, since the resin-coated carrier has a large surface area, the bulk density is low, and when the toner density per weight is the same at the developing sleeve and the nip portion of the photosensitive member, the volume occupied by carrier particles having a strong magnetic force increases and high-speed development is achieved. In this case, it is considered that the toner can be sufficiently held and conveyed.

When B1 / B2 is less than 6.0, the effect of reducing wear of the resin coating layer by the conductive fine particles is small, the film scraping progresses with time, the resistance decreases, the bulk density of the core material is low, and the magnetic force Carrier scattering is likely to occur.
On the other hand, if B1 / B2 exceeds 8.0, the toner spent on the resin coating layer tends to advance and the charging ability tends to decrease, so that density fluctuations are likely to occur, and ghost development and halo may deteriorate.

  The core material particle is not particularly limited as long as it is a magnetic material, but is not limited to ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite, and ferrite; various alloys and compounds; Examples thereof include dispersed resin particles. Of these, Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr ferrite, and the like are preferable from the viewpoint of environmental considerations.

The BET specific surface area of the core particles can be adjusted by a conventionally known method. For example, as described in JP-A No. 2000-172017, a method of adjusting the firing temperature, JP-A No. 2012-63718, or the like. Can be adjusted by controlling the pulverized particle size of the magnetic material.

<Carrier properties>
The carrier particles of the present invention preferably have a volume average particle size of 32 μm or more and 40 μm or less. When the volume average particle diameter of the carrier particles is less than 32 μm, carrier adhesion may occur. When the volume average particle diameter exceeds 40 μm, the reproducibility of image details may be reduced and a fine image may not be formed.
The volume average particle diameter can be measured using, for example, a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

  The carrier of the present invention preferably has a volume resistivity of 9 to 13 (Log Ω · cm). If the volume resistivity is less than 9 (Log Ω · cm), carrier adhesion may occur in the non-image area, and if it exceeds 13 (Log Ω · cm), the edge effect may be at an unacceptable level.

  The volume resistivity can be measured using the cell shown in FIG. Specifically, first, a carrier (3) is placed in a cell composed of a fluororesin container (2) in which an electrode (1a) and an electrode (1b) having a surface area of 2.5 cm × 4 cm are accommodated at a distance of 0.2 cm. ) And is tapped 10 times with a drop height of 1 cm and a tapping speed of 30 times / minute. Next, a DC voltage of 1000 V is applied between the electrodes (1a) and (1b), and a resistance value r [Ω] after 30 seconds is measured using a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Company). From the following formula 2, the volume resistivity [Ω · cm] can be calculated.

<Developer>
The carrier of the present invention can be mixed with toner and used as a two-component developer.
The toner contains a binder resin and a colorant, and may be a monochrome toner or a color toner. Further, the toner particles may contain a release agent in order to be applied to an oilless system in which toner fixing prevention oil is not applied to the fixing roller. Such toner generally tends to cause filming. However, since the carrier of the present invention can suppress filming, the developer of the present invention maintains good quality for a long time. Can do.

  Furthermore, color toners, in particular yellow toners, generally have a problem that color stains occur due to scraping of the resin coating layer of the carrier, but the developer of the present invention can suppress the occurrence of color stains, It can be used by mixing with color toner.

  The toner can be produced using a known method such as a pulverization method or a polymerization method. For example, when a toner is manufactured using a pulverization method, first, the melt-kneaded product obtained by kneading the toner material is cooled, and then pulverized and classified to produce a toner. In order to further improve transferability and durability, a toner added with an external additive may be used.

  The apparatus for kneading the toner material is not particularly limited, but is a batch type two roll; a Banbury mixer; a KTK type twin screw extruder (manufactured by Kobe Steel), a TEM type twin screw extruder (manufactured by Toshiba Machine Co., Ltd.). ) Continuous twin screw extruders such as a twin screw extruder (manufactured by KCK), a PCM type twin screw extruder (manufactured by Ikekai Tekko), a KEX type twin screw extruder (manufactured by Kurimoto Iron Works); Examples thereof include a continuous single-screw kneader such as a kneader (manufactured by Buss).

  Further, when the cooled melt-kneaded product is pulverized, it is roughly pulverized using a hammer mill, a rotoplex, etc., and then finely pulverized using a fine pulverizer using a jet stream, a mechanical pulverizer or the like. be able to. In addition, it is preferable to grind | pulverize so that an average particle diameter may be set to 3-15 micrometers.

Furthermore, when classifying the crushed melt-kneaded material, a wind classifier or the like can be used. In addition, it is preferable to classify so that the average particle diameter of the base particles is 5 to 20 μm.
When the external additive is added, the external additive adheres to the surface of the toner base particles while being crushed by mixing and stirring using a mixer.

The binder resin is not particularly limited, but is a homopolymer of styrene such as polystyrene, poly-p-styrene, polyvinyltoluene or the like and a substituted product thereof;
Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer Styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl Styrene copolymers such as methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid ester copolymer;
Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aromatic A hydrocarbon resin, an aromatic petroleum resin, etc. are mentioned, You may use 2 or more types together.

The binder resin for pressure fixing is not particularly limited, but polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene;
Ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, Olefin copolymers such as ionomer resins;
An epoxy resin, polyester, styrene-butadiene copolymer, polyvinyl pyrrolidone, methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin and the like may be used, and two or more kinds may be used in combination.

Although it does not specifically limit as a coloring agent (pigment or dye), Cadmium yellow, mineral fast yellow, nickel titanium yellow, Navels yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, Yellow pigments such as permanent yellow NCG, tartrazine lake;
Orange pigments such as molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK;
Red pigments such as Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B;
Purple pigments such as Fast Violet B and Methyl Violet Lake;
Blue pigments such as cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, indanthrene blue BC;
Green pigments such as chrome green, chromium oxide, pigment green B, malachite green lake, etc .;
Examples include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, and black pigments such as metal salt azo dyes, metal oxides, and complex metal oxides. You may use together.

  The release agent is not particularly limited, but includes polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, ester wax and the like. Two or more kinds may be used in combination.

  The toner may further contain a charge control agent. The charge control agent is not particularly limited, but nigrosine; an azine dye having an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627); I. Basic Yellow 2 (C.I. 41000), C.I. I. Basic Yellow 3, C.I. I. Basic Red 1 (C.I. 45160), C.I. I. Basic Red 9 (C.I. 42500), C.I. I. Basic Violet 1 (C.I. 42535), C.I. I. Basic Violet 3 (C.I. 42555), C.I. I. Basic Violet 10 (C.I. 45170), C.I. I. Basic Violet 14 (C.I. 42510), C.I. I. Basic Blue 1 (C.I. 42025), C.I. I. Basic Blue 3 (C.I. 51005), C.I. I. Basic Blue 5 (C.I. 42140), C.I. I. Basic Blue 7 (C.I. 42595), C.I. I. Basic Blue 9 (C.I. 52015), C.I. I. Basic Blue 24 (C.I. 52030), C.I. I. Basic Blue 25 (C.I. 52025), C.I. I. Basic Blue 26 (C.I. 44045), C.I. I. Basic Green 1 (C.I. 42040), C.I. I. Basic dyes such as Basic Green 4 (C.I. 42000); lake pigments of these basic dyes; I. Solvent Black 8 (C.I. 26150), quaternary ammonium salts such as benzoylmethylhexadecyl ammonium chloride and decyltrimethyl chloride; dialkyltin compounds such as dibutyl and dioctyl; dialkyltin borate compounds; guanidine derivatives; vinyl having an amino group Polyamine resins such as polycondensation polymers and condensation polymers having amino groups; described in JP-B-41-20153, JP-B-43-27596, JP-B-44-6397, and JP-B-45-26478 Metal complex salts of monoazo dyes; salicylic acids described in JP-B-55-42752 and JP-B-59-7385; dialkylsalicylic acid, naphthoic acid, dicarboxylic acid Zn, Al, Co, Cr, Fe, etc. Metal complexes of Examples thereof include honed copper phthalocyanine pigments; organic boron salts; fluorine-containing quaternary ammonium salts; calixarene compounds, and the like. For color toners other than black, white metal salts of salicylic acid derivatives are preferred.

The external additive is not particularly limited, but inorganic particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride, etc .; poly having an average particle size of 0.05 to 1 μm obtained by a soap-free emulsion polymerization method Examples thereof include resin particles such as methyl methacrylate particles and polystyrene particles, and two or more kinds may be used in combination.
Among these, metal oxide particles such as silica and titanium oxide whose surfaces are hydrophobized are preferable. Furthermore, by using a combination of hydrophobized silica and hydrophobized titanium oxide, the amount of added hydrophobized titanium oxide is higher than that of hydrophobized silica. A toner having excellent charging stability can be obtained.

<Replenishment developer>
By using the carrier of the present invention as a replenishment developer composed of a carrier and a toner and applying it to an image forming apparatus that forms an image while discharging excess developer in the developing device, a stable image can be obtained over a very long period of time. Quality is obtained.
That is, the deteriorated carrier in the developing device and the non-deteriorated carrier in the replenishing developer are replaced, and the charge amount is kept stable for a long period of time, so that a stable image can be obtained.
This method is particularly effective when printing a large image area. When printing a large image area, carrier charge deterioration due to toner spent on the carrier is the main carrier deterioration. However, when this method is used, the carrier replenishment amount increases when the image area is large, and the deteriorated carrier is replaced. Increases frequency. Thereby, a stable image can be obtained over an extremely long period of time.

  The mixing ratio of the replenishment developer is preferably 2 to 50 parts by mass of toner with respect to 1 part by mass of the carrier. When the amount of toner is less than 2 parts by mass, the amount of replenishment carrier is excessive, the carrier is excessively supplied, and the carrier concentration in the developing device becomes too high, so that the charge amount of the developer tends to increase. Further, when the developer charge amount increases, the developing ability decreases and the image density decreases. On the other hand, if the amount exceeds 50 parts by mass, the carrier ratio in the replenishment developer decreases, so that the replacement of carriers in the image forming apparatus decreases, and the effect on carrier deterioration cannot be expected.

<Image forming method>
The image forming method of the present invention uses the developer of the present invention to form an electrostatic latent image on the electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier. Development to form a toner image, a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a step of fixing the toner image transferred to the recording medium.

<Process cartridge>
FIG. 4 shows an example of the process cartridge of the present invention. The process cartridge (10) comprises a photoreceptor (11), a charging device (12) for charging the photoreceptor (11), and an electrostatic latent image formed on the photoreceptor (11) using the developer of the present invention. A developing device (13) for developing and forming a toner image and a cleaning device (after removing the toner remaining on the photoconductor (11) after transferring the toner image formed on the photoconductor (11) to a recording medium. 14) is integrally supported, and the process cartridge (10) is detachable from a main body of an image forming apparatus such as a copying machine or a printer.

  Hereinafter, a method for forming an image using the image forming apparatus equipped with the process cartridge (10) will be described. First, the photosensitive member (11) is rotationally driven at a predetermined peripheral speed, and the charging device (12) uniformly charges the peripheral surface of the photosensitive member (11) to a predetermined positive or negative potential. Next, exposure light is irradiated onto the peripheral surface of the photoreceptor (11) from an exposure apparatus (not shown) such as a slit exposure type exposure apparatus or an exposure apparatus that performs scanning exposure with a laser beam, and electrostatic latent images are sequentially formed. The Further, the electrostatic latent image formed on the peripheral surface of the photoconductor (11) is developed by the developing device (13) using the developer of the present invention to form a toner image. Next, the toner image formed on the peripheral surface of the photoconductor (11) is synchronized with the rotation of the photoconductor (11), and the photoconductor (11) and the transfer device (not shown) are fed from the paper feed unit (not shown). ) Are sequentially transferred onto the transfer paper fed during (). Further, the transfer paper onto which the toner image has been transferred is separated from the peripheral surface of the photoreceptor (11), introduced into a fixing device (not shown) and fixed, and then copied as a copy (copy) of the image forming apparatus. Printed out. On the other hand, after the toner image is transferred, the surface of the photoconductor (11) is cleaned by the cleaning device (14) to remove the remaining toner, and then the charge is removed by a static eliminator (not shown). Used for image formation.

<Image forming apparatus>
The image forming apparatus of the present invention includes an electrostatic latent image carrier, a charging unit that charges the latent image carrier, an exposure unit that forms an electrostatic latent image on the latent image carrier, and the electrostatic latent image. Developing means for developing the electrostatic latent image formed on the image carrier using a developer to form a toner image, and transferring the toner image formed on the electrostatic latent image carrier to a recording medium Transfer means, and fixing means for fixing the toner image transferred to the recording medium, and other means appropriately selected as necessary, for example, static elimination means, cleaning means, recycling means, control The developer of the present invention is used as a developer.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these. “Parts” represents parts by weight.

[Core Material Production Example 1]
MnCO ₃ , Mg (OH) ₂ , Fe ₂ O ₃ , and SrCO ₃ powder were weighed and mixed to obtain a mixed powder.
The mixed powder was calcined in a heating furnace at 800 ° C. for 1 hour in the air atmosphere, and the obtained calcined product was cooled and pulverized to obtain a powder having a particle size of 3 μm or less. This powder was made into a slurry by adding 1 wt% of a dispersant together with water, and the slurry was supplied to a spray dryer and granulated to obtain a granulated product having an average particle size of about 40 μm. This granulated product was loaded into a firing furnace and fired at 1120 ° C. for 4 hours in a nitrogen atmosphere.

The obtained fired product was pulverized with a pulverizer, and the particle size was adjusted by sieving to obtain spherical ferrite particles C1 having a volume average particle size of about 35 μm and a BET specific surface area of 0.13 m ² / g.

The volume average particle size is set to a material refractive index of 2.42, a solvent refractive index of 1.33, and a concentration of about 0.06 in water using a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.). Measured.

The BET specific surface area of the core particles can be measured using an automatic specific surface area / pore distribution measuring device (TriStar 3000: manufactured by Shimadzu Corporation). In the present invention, the BET specific surface area was measured by this method. That is, about 5.0 g of a sample is weighed in a sample cell, and this is vacuum-dried for 24 hours with a pretreatment smart prep (manufactured by Shimadzu Corporation) to remove impurities and moisture on the sample surface. The pretreated sample is set in TriStar 3000, and the relationship between the nitrogen gas adsorption amount and the relative pressure is obtained. From this relationship, the BET specific surface area of the sample can be obtained by the BET multipoint method.

[Core material production example 2]
Spherical ferrite particles C2 having a volume average particle size of about 35 μm and a BET specific surface area of 0.16 m ² / g were obtained in exactly the same manner as C1, except that calcining was performed at 850 ° C. in the adjustment of core production example 1.

[Core Material Production Example 3]
Spherical ferrite particles C3 having a volume average particle diameter of about 35 μm and a BET specific surface area of 0.20 m ² / g were obtained in exactly the same manner as C1, except that calcining was performed at 900 ° C. in the preparation of core material production example 1.

[Core Material Production Example 4]
Spherical ferrite particles C4 having a volume average particle diameter of about 35 μm and a BET specific surface area of 0.12 m ² / g were obtained in exactly the same manner as C1, except that calcining was performed at 750 ° C. in the preparation of core material production example 1.
[Core Material Production Example 5]
Spherical ferrite particles C5 having a volume average particle diameter of about 35 μm and a BET specific surface area of 0.21 m ² / g were obtained in exactly the same manner as C1, except that calcining was carried out at 950 ° C. in the preparation of core material production example 1.

[Conductive fine particle production example 1]
100 g of aluminum oxide (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.) was dispersed in 1 liter of water to form a suspension, and this liquid was heated to 70 ° C. A suspension of 85 g of stannic chloride and 3.8 g of phosphorus pentoxide in 1.7 liters of 2N hydrochloric acid and 12 wt% aqueous ammonia was added to the suspension so that the suspension had a pH of 7-8. It was added dropwise over a period of 40 minutes.
After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles P1 having an average particle size of 0.35 μm and a powder specific resistance of 8 Ω · cm.

The average particle size was measured using Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.) in water at a material refractive index of 1.66 and a solvent refractive index of 1.33.
In addition, the powder specific resistance of the conductive fine particles was converted to specific resistance by measuring the electrical resistance value using a LCR meter manufactured by Yokogawa Hewlett-Packard Co. after compression molding the sample powder at 230 kg / cm ² .

[Resin synthesis example 1]
300 g of toluene was charged into a flask equipped with a stirrer, and the temperature was raised to 90 ° C. under a nitrogen gas stream.
Then this
_{CH 2 = CMe-COO-C} 3 H 6 -Si (OSiMe 3) 3
(In the formula, Me is a methyl group.)
3-methacryloxypropyltris (trimethylsiloxy) silane 84.4 g (200 mmol: Silaplane TM-0701T / manufactured by Chisso Corporation), 3-methacryloxypropylmethyldiethoxysilane 39 g (150 mmol), methacrylic acid A mixture of 65.0 g (650 mmol) of methyl and 0.58 g (3 mmol) of 2,2′-azobis-2-methylbutyronitrile was added dropwise over 1 hour.
After completion of the dropwise addition, a solution prepared by dissolving 0.06 g (0.3 mmol) of 2,2′-azobis-2-methylbutyronitrile in 15 g of toluene was further added (2,2′-azobis-2-methylbutyrate). A total amount of ronitrile (0.64 g = 3.3 mmol) was mixed at 90 to 100 ° C. for 3 hours and radical copolymerized to obtain a methacrylic copolymer R1.

[Example 1]
[Carrier Production Example 1]
(Carrier coating layer)
The following materials were dispersed with a homomixer for 10 minutes to obtain a mixed coating film forming solution of acrylic resin and silicon resin.

・ Methacrylic copolymer R1 resin solution (solid content 50 wt%) 51.3 parts by weight ・ Guanamine solution (solid content 70 wt%) 14.6 parts by weight ・ Titanium catalyst [solid content 60 wt% (TC-750: Matsumoto Fine Chemical Co., Ltd.)]
4 parts by weight Silicone resin solution [solid content 20% by weight (SR2410: manufactured by Toray Dow Corning Silicone)] 648 parts by weight Aminosilane [solid content 100% by weight (SH6020: manufactured by Toray Dow Corning Silicone)] 3.2 parts by weight, conductive fine particles P1 80 parts by weight, toluene 1000 parts by weight

Using C1: 5000 parts by weight as the core material, the above coating film forming solution was applied on the surface of the core material to a film thickness of 0.30 μm by a Spira coater (manufactured by Okada Seiko Co., Ltd.) at a coater internal temperature of 55 ° C. and dried. did. The obtained carrier was fired in an electric furnace at 200 ° C. for 1 hour.
After cooling, the ferrite powder bulk was crushed using a sieve having an aperture of 63 μm to obtain a carrier 1 having a BET specific surface area of 0.8 m 2 / g, a volume average particle size of 36 μm, and a volume resistivity of 13 LogΩcm.

The BET specific surface area of the carrier particles can be measured using an automatic specific surface area / pore distribution measuring device (TriStar 3000: manufactured by Shimadzu Corporation). In the present invention, the BET specific surface area was measured by this method.
That is, about 5.0 g of a sample is weighed in a sample cell, and this is vacuum-dried for 24 hours with a pretreatment smart prep (manufactured by Shimadzu Corporation) to remove impurities and moisture on the sample surface. The pretreated sample is set in TriStar 3000, and the relationship between the nitrogen gas adsorption amount and the relative pressure is obtained. From this relationship, the BET specific surface area of the sample can be obtained by the BET multipoint method.

  The volume average particle size is set to a material refractive index of 2.42, a solvent refractive index of 1.33, and a concentration of about 0.06 in water using a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.). Measured.

  The volume resistivity is determined from the fluororesin container (2) containing the electrode (1a) and the electrode (1b) having a surface area of 2.5 cm × 4 cm with a distance of 0.2 cm using the cell shown in FIG. After filling the cell with carrier (3), tapping 10 times with a drop height of 1 cm and a tapping speed of 30 times / minute, a DC voltage of 1000 V was applied between the electrodes (1a) and (1b). The resistance value r [Ω] 30 seconds after application was measured using a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Company), and the volume resistivity [Ω · cm] was calculated from the following equation 2.

[Example 2]
[Carrier Production Example 2]
In Carrier Production Example 1, a carrier having a BET specific surface area of 0.9 m ² / g, a volume average particle size of 36 μm, and a volume resistivity of 10 LogΩcm, except that the conductive fine particles P1 are 200 parts by weight. 2 was obtained.

[Example 3]
[Carrier Production Example 3]
In Carrier Production Example 1, a carrier 3 having a BET specific surface area of 1.1 m ² / g, a volume average particle size of 36 μm, and a volume resistivity of 13 LogΩcm is obtained in the same manner as in the carrier 1 except that the core particle is C2. It was.

[Example 4]
[Carrier Production Example 4]
A carrier having a BET specific surface area of 1.2 m ² / g, a volume average particle size of 36 μm, and a volume resistivity of 12 LogΩcm, exactly as in the carrier 3 except that the conductive fine particles P1 were changed to 140 parts by weight in the carrier production example 3. 4 was obtained.

[Example 5]
[Carrier Production Example 5]
In Carrier Production Example 3, except that the conductive fine particles P1 were 200 parts by weight, the BET specific surface area was 1.3 m ^ 2 / g, the volume average particle size was 36 μm, and the volume specific resistance was 10 LogΩcm, except that the conductive fine particles P1 were 200 parts by weight. Carrier 5 was obtained.

[Example 6]
[Carrier Production Example 6]
In Carrier Production Example 1, a carrier 6 having a BET specific surface area of 1.5 m ² / g, a volume average particle size of 36 μm, and a volume specific resistance of 13 LogΩcm is obtained in the same manner as in the carrier 1 except that the core particle is C3. It was.

[Example 7]
[Carrier Production Example 7]
In Carrier Production Example 2, a carrier 7 having a BET specific surface area of 1.6 m ² / g, a volume average particle size of 36 μm, and a volume specific resistance of 10 LogΩcm is obtained in the same manner as in the carrier 2 except that the core particle is C3. It was.

[Example 8]
[Carrier Production Example 8]
In Carrier Production Example 3, a carrier having a BET specific surface area of 1.1 m ² / g, a volume average particle size of 36 μm, and a volume resistivity of 13 Log Ωcm, except that the conductive fine particles P1 are 75 parts by weight. 8 was obtained.

[Example 9]
[Carrier Production Example 9]
In Carrier Production Example 3, a carrier having a BET specific surface area of 1.3 m ² / g, a volume average particle size of 36 μm, and a volume resistivity of 10 LogΩcm, except that the conductive fine particles P1 are 210 parts by weight. 9 was obtained.

[Example 10]
[Carrier Production Example 10]
In Carrier Production Example 1, the BET specific surface area was 0.8 m ² / g, the volume average particle size was 36 μm, exactly the same as Carrier 1 except that the core particles were C4 and the conductive fine particles P1 were 85 parts by weight. A carrier 10 having a volume resistivity of 13 LogΩcm was obtained.

[Example 11]
[Carrier Production Example 11]
In Carrier Production Example 1, the BET specific surface area was 1.6 m ² / g, the volume average particle size was 36 μm, exactly the same as Carrier 1, except that the core particles were C5 and the conductive fine particles P1 were 175 parts by weight. A carrier 11 having a volume resistivity of 11 LogΩcm was obtained.

[Comparative Example 1]
[Carrier Production Example 1 ']
A carrier having a BET specific surface area of 0.7 m ² / g, a volume average particle size of 36 μm, and a volume resistivity of 13 LogΩcm, exactly as in the carrier 1 except that the conductive fine particles P1 were changed to 75 parts by weight. 1 'was obtained.

[Comparative Example 2]
[Carrier Production Example 2 ']
A carrier having a BET specific surface area of 1.7 m ² / g, a volume average particle size of 36 μm, and a volume specific resistance of 10 LogΩcm, exactly as in the carrier 6, except that the conductive fine particles P1 were changed to 210 parts by weight in the carrier production example 6. 2 'was obtained.

[Comparative Example 3]
[Carrier Production Example 3 ']
A carrier having a BET specific surface area of 0.7 m ² / g, a volume average particle diameter of 36 μm, and a volume resistivity of 13 LogΩcm, exactly as in the carrier 10, except that the conductive fine particle P1 was changed to 80 parts by weight in the carrier production example 10. 3 'was obtained.

[Comparative Example 4]
[Carrier Production Example 4 ']
In Carrier Production Example 11, a carrier having a BET specific surface area of 1.7 m ² / g, a volume average particle size of 36 μm, and a volume resistivity of 10 LogΩcm, except that the conductive fine particles P1 were changed to 160 parts by weight. 4 'was obtained.

The obtained carrier properties are shown in Table 1.

<Example of toner production>
[Synthesis Example of Polyester Resin A]
443 parts of PO adduct of bisphenol A (hydroxyl value 320), 135 parts of diethylene glycol, 422 parts of terephthalic acid, and 2.5 parts of dibutyltin oxide are placed in a reaction vessel equipped with a thermometer, stirrer, cooler and nitrogen introduction tube. Then, the reaction was carried out at 200 ° C. until the acid value reached 10 to obtain [Polyester Resin A]. The resin had a Tg of 63 ° C. and a peak number average molecular weight of 6000.

[Synthesis example of polyester resin B]
443 parts of PO adduct of bisphenol A (hydroxyl value 320), 135 parts of diethylene glycol, 422 parts of terephthalic acid, and 2.5 parts of dibutyltin oxide are placed in a reaction vessel equipped with a thermometer, stirrer, cooler and nitrogen introduction tube. Then, the reaction was carried out at 230 ° C. until the acid value became 7, to obtain [Polyester Resin B]. The resin had a Tg of 65 ° C. and a peak number average molecular weight of 16000.

[Manufacture of base toner particles 1]
· Polyester resin A · · · 40 parts · Polyester resin B · · · 60 parts · Carnauba wax · · · 1 part · Carbon black (# 44 manufactured by Mitsubishi Chemical Corporation) · · · 15 parts The materials are mixed with a Henschel mixer (Mitsui Mining Co., Ltd., Henschel 20B, 1500 rpm for 3 minutes) and kneaded with a single-screw kneader (Buss Co., Ltd. small bus-co-kneader) under the following conditions (set temperature) : Feeder: 2 kg / Hr) at an inlet portion of 100 ° C. and an outlet portion of 50 ° C., and [Base toner A1] was obtained.
Further, the [base toner A1] was kneaded and then cooled by rolling, pulverized by a pulverizer, and further an I-type mill (IDS-2 type manufactured by Nippon Pneumatic Co., Ltd., using a flat impact plate, air pressure: 6.8 atm). / Cm ² , feed amount: 0.5 kg / hr) was finely pulverized, and further classified (132MP manufactured by Alpine) to obtain [base toner particles 1].

(External additive treatment)
To 100 parts of “base toner particle 1”, 1.0 part of hydrophobic silica fine particles (R972: manufactured by Nippon Aerosil Co., Ltd.) was added as an external additive and mixed with a Henschel mixer to obtain toner particles (hereinafter “toner toner”). 1 ”).

[Production of Developers 1-11, 1′-4 ′]
7.0 parts of the toner 1 (7.2 μm) obtained in the toner production example is added to the carriers 1 to 11, 1 ′ to 4 ′ (93 parts) obtained in the carrier production example, and 20 parts by a ball mill. Developers 1-11 and 1'-4 'were prepared by stirring for a minute.

(Developer characteristics evaluation)
Using the developer thus obtained, image evaluation was carried out using a Ricoh Pro C901 (Ricoh Digital Color Copier / Printer Combined Machine) manufactured by Ricoh. Specifically, first, using the developers 1 to 11, 1 'to 4' of Examples and Comparative Examples, and the toner 1, an image area ratio of 20% and initial and 1 million sheets of the carrier after running. The amount of charge and the volume resistivity were measured, and the amount of decrease in charge and the amount of change in volume resistivity were calculated.

The charge amount (Q1) of the initial carrier is such that the carrier 1 to 11, 1 'to 4' and the toner 1 are mixed at a mass ratio of 93: 7, and a frictionally charged sample is blow-off device TB-200. (Toshiba Chemical Co., Ltd.) was used for measurement.
The charge amount (Q2) of the carrier after running 1 million sheets was measured in the same manner as described above except that the carrier from which the toner of each color in the developer after running was removed using a blow-off device. The target value of the change amount of the charge amount is 10 (μC / g) or less.

On the other hand, the volume specific resistance (LogR1) of the initial carrier is a common logarithmic value of the volume specific resistance of the carrier measured in the same manner as [Volume Specific Resistance].
The volume specific resistance (LogR2) of the carrier after running 1,000,000 sheets was measured in the same manner as described above except that the carrier from which the toner of each color in the developer after running was removed using a blow-off device.
Note that the target value of the volume resistivity is an absolute value of less than 2.0 (Log Ωcm).

Table 2 shows the developer evaluation results.

<Real machine quality evaluation>
In the image quality characteristic test, an image was formed under the following development conditions using a Ricoh Pro C901 (Ricoh Digital Color Copier / Printer Combined Machine) manufactured by Ricoh.
・ Development gap (photosensitive member-developing sleeve): 0.3 mm
・ Doctor gap (developing sleeve-doctor): 0.65mm
-Photoconductor linear velocity: 440 mm / sec
(Development sleeve linear velocity) / (photosensitive member linear velocity): 1.80
-Write density: 600 dpi
・ Charging potential (Vd): -600V
-Potential after exposure of the portion corresponding to the image portion (solid document): -100V
Development bias: DC-500V / AC bias component: 2KHz, -100V to -900V, 50% duty

(1) Solid part image density: The center of a solid part (Note 1) of 30 mm × 30 mm in the above development conditions was measured at five locations with an X-Rite 938 spectrocolorimetric densitometer, and an average value was obtained.
Note 1; development potential equivalent to 400V = (exposure portion potential−development bias DC) = − 100V − (− 500V)

The ID difference after the initial and 1 million sheets was evaluated according to the following criteria.
0 or more and less than 0.2: ◎ (very good)
0.2 to less than 0.3: ○ (good)
0.3 or more and less than 0.4: △ (can be used)
0.4 or more: × (defect)

(2) Highlight portion image density: The center of a 30 mm × 30 mm highlight portion (Note 2) in the above development conditions was measured at five locations with an X-Rite 938 spectrophotometric densitometer, and an average value was obtained.
Note 2: Location corresponding to 150 V development potential = (highlight portion potential-development bias DC) = -350 V-(-500 V)

The ID difference after the initial and 1 million sheets was evaluated according to the following criteria.
0 or more and less than 0.2: ◎ (very good)
0.2 to less than 0.3: ○ (good)
0.3 or more and less than 0.4: △ (can be used)
0.4 or more: × (defect)

(3) Granularity: The granularity (brightness range: 50 to 80) defined by the following formula was measured, and the numerical values were evaluated by replacing them with ranks as follows.
Granularity = exp (aL + b) ∫ (WS (f)) 1/2 · VTF (f) df
L: Average brightness f: Spatial frequency (cycle / mm)
WS (f): brightness fluctuation power spectrum VTF (f): visual spatial frequency characteristics a, b: coefficient

0 or more and less than 0.2: ◎ (very good)
0.2 to less than 0.3: ○ (good)
0.3 or more and less than 0.4: △ (can be used)
0.4 or more: × (defect)

(4) Carrier adhesion (solid part)
When carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, resulting in a decrease in image quality. Even if carrier adhesion occurs on the photoconductor, only a part of the carrier is transferred to the paper, and thus evaluation was made by the following method.
A solid image (30 mm × 30 mm) of Ricoh Pro C901 under the above-mentioned development conditions (charge potential (Vd): −600 V, potential after exposure of a portion corresponding to an image portion (solid original): −100 V, development bias: DC-500 V) The number of carriers adhering to the toner was counted on the photoconductor to evaluate solid carrier adhesion.

The symbols described in the table are ◎: very good, ○: good, Δ: usable, ×: poor.

(5) Carrier adhesion (edge)
When carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, resulting in a decrease in image quality. Even if carrier adhesion occurs on the photoconductor, only a part of the carrier is transferred to the paper, and thus evaluation was made by the following method.
Under the developing conditions of a charging potential (Vd) of −600 V, an exposure portion potential of −100 V, and a developing bias (Vb) of DC-400 V, that is, a background potential of 200 V, two dot lines (100 lpi) in the sub-scanning direction on the photoreceptor. / Inch) image was formed.
Next, the two-dot line developed on the photoconductor was transferred with an adhesive tape (area 100 cm ² ), and the number was counted to evaluate the carrier adhesion.

The symbols described in the table are ◎: very good, ○: good, Δ: usable, x: defective (x is an unacceptable level).

(6) Evaluation method of ghost image For ghost images, after printing 100K of a character chart with an image area of 8% (size of one character; about 2 mm x 2 mm), the vertical band chart shown in FIG. The density difference between one round (a) and one round after (b) was determined by X-Rite938 (manufactured by X-Rite), and the average density difference between the center, rear, and front measurements was taken as ΔID, and was ranked below.

A: Very good, B: Good, B: Acceptable, B: Unusable for practical use A: B, B, C: Passed and x: Fail.
A: 0.01 ≧ ΔID
○: 0.01 <ΔID ≦ 0.03
Δ: 0.03 <ΔID ≦ 0.06
×: 0.06 <ΔID

(7) Evaluation of hello image The image pattern shown in FIG. 4 is output, and the white area around the solid image is measured, and the image in the hello state is evaluated as x when a white area of 0.1 [mm] or more occurs. Evaluation was made with less than 0.1 mm.

Table 3 shows the results after 1 million sheets.

(About Figure 1)
1a Electrode 1b Electrode 2 Fluororesin 3 Carrier (About FIG. 2)
10 Process Cartridge 11 Photoconductor 12 Charging Device 13 Developing Device 14 Cleaning Device

Japanese Patent Laid-Open No. 55-127469 Japanese Patent Laid-Open No. 55-157751 JP-A-56-140358 JP-A-57-96355 JP 57-96356 A JP 58-207054 A JP-A-61-1110161 JP-A-62-273576 JP 2005-309184 A Japanese Patent No. 4544099 Japanese Patent No. 4621639 In Japanese Patent Application Laid-Open No. 2008-40271 JP 2011-253007 A JP 2006-259179 A JP 2009-53545 A JP 2009-300531 A

Claims (10)

A carrier for electrostatic latent image developer, wherein the surface of magnetic core material particles is coated with a resin coating layer containing conductive fine particles, and has a BET specific surface area of 0.8 m ² / g or more and 1.6 m ² / The carrier for an electrostatic latent image developer, wherein the carrier is not more than g.   The carrier for an electrostatic latent image developer according to claim 1, wherein an average primary particle size of the conductive fine particles is from 0.35 μm to 0.65 μm.   The electrostatic latent image developer carrier according to claim 1, wherein the conductive fine particles are contained in an amount of 0.016 parts by weight to 0.040 parts by weight with respect to 1 part by weight of the core particles. . When the BET specific surface area of the carrier is (B1) and the BET specific surface area of the core material is (B2), the specific surface area ratio (B1 / B2) satisfies the relationship of the following formula (1). The carrier for an electrostatic latent image developer according to any one of claims 1 to 3.

  A two-component developer comprising the carrier and the toner according to claim 1.   The developer according to claim 5, wherein the toner is a color toner.   A replenishment developer containing a carrier and a toner, the toner containing 2 to 50 parts by weight of toner with respect to 1 part by mass of the carrier, wherein the carrier is the carrier according to any one of claims 1 to 4. A developer for replenishment characterized by the above.   An electrostatic latent image carrier, a charging unit for charging the latent image carrier, an exposure unit for forming an electrostatic latent image on the latent image carrier, and an electrostatic latent image carrier formed on the electrostatic latent image carrier. A developing unit that develops an electrostatic latent image using the developer according to claim 5 to form a toner image, and records the toner image formed on the electrostatic latent image carrier. An image forming apparatus comprising: transfer means for transferring to a medium; and fixing means for fixing a toner image transferred to the recording medium.   The developer according to claim 5, wherein an electrostatic latent image carrier, a charging member that charges the surface of the photosensitive member, and an electrostatic latent image formed on the electrostatic latent image carrier. A process cartridge comprising: a developing unit that uses and develops; and a cleaning member that cleans the electrostatic latent image carrier.   The developer according to any one of claims 5 to 7, comprising: forming an electrostatic latent image on the electrostatic latent image carrier; and forming the electrostatic latent image formed on the electrostatic latent image carrier. Developing the toner image to form a toner image; transferring the toner image formed on the electrostatic latent image carrier to a recording medium; fixing the toner image transferred to the recording medium; An image forming method comprising:

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